How to choose Couplings:Choose couplings carefully. There are dozens of important inputs for couplings selection, including service factor. This key variable specifies the maximum torque a coupling can endure If torque is constant, the service factor mayb e as low as 1.0.In contrast, heavy shock loads with some negative torques require the highest service factory of 3.0.System compatibility, operating environment, and service requirements also figure into coupling slection.